Jay Cost On House Probability
Jay Cost just published a great article, “What Does the Money Tell Us About Tuesday?” It is rather lengthy and technical so as a public service I am going to distill out the main points because it ties into what I have been writing about probability:
This might seem like a lot for the Republicans to defend, and from a certain perspective it is. However, whether or not the Democrats pick up control of the House by plucking a net of 15 of these districts really depends upon the probability of flipping we assign to each race. If, for instance, both parties have an equal shot in every seat, we should expect the Democrats to net 16 to 17 seats – and the Democrats have a 73% chance of taking the House. If the Democrats have a 40% chance in every seat, we should expect them to net 12 to 13 seats – and they have a 25% chance of taking the House. If the Democrats have a 60% chance in every seat, we should expect them to net 20 to 21 seats – and they have a 97% chance of taking the House.
This is the main reason I am skeptical of the “wave,” i.e. a net of 25 or more for the Democrats. Even if we give the Democrats 2/1 odds in each contest, with this battlefield there is still only a 35% chance that they net 25 or more seats.
In my opinion, a “toss up” seat from an incumbent is not a 50/50 proposition. I subscribe to the 40% probability, based on extensive historical analysis, that Jay lists above. There is a 75% probability that the Republicans will maintain the House by a margin of 2/3 seats.
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